Monoclonal gammopathy of undetermined significance (MGUS)
Asymptomatic premalignant state
Common in elderly population (~10% in patients >75 years old)
Paraprotein <30g/L (<3g/dL)
Plasma cells <10% on bone marrow
No CRAB syndromes (see below)
No other B-cell proliferation disorder
No treatment needed, but must be monitored as 1-1.5% will progress to Multiple Myeloma per year
Multiple Myeloma
Neoplastic proliferation of a single plasma cell lineage aka M-protein (Usually of the IgG or IgA type)
Incidence is increased after age 50
Paraprotein >30g/L (>3g/dL) [serum and/or urine]
Plasma cells >10% on bone marrow
CRAB SYMPTOMS
HyperCalcemia: Due to bone destruction from lytic bone lesions
Renal Failure: Immunoglobulin precipitation in renal tubules leads to tubular casts of Bence Jones protein
Anemia: Normocytic normochromic. Also leukopenia, thrombocytopenia (look for rouleaux formation on peripheral smear—hyperglobulinemia causes the RBCs to stick together)
Bone pain: Due to osteolytic lesions and vertebral fractures
Treated with bisphosphonates, steroids, chemotherapy (If below age 65 consider autologous hematopoietic stem-cell transplantation).
Waldenström’s macroglobulinemia
Malignant proliferation of plasmacytoid lymphocytes
IgM >50g/L (5 g/dL)
Bence Jones proteinuria in 10% of cases
Hyperviscosity syndrome (due to paraproteinemia of large sized IgM): visual changes due to retinopathy, headache, vertigo, mucosal bleeding, seizures and coma
Other Clinical features: constitutional symptoms, splenomegaly, anemia and lymphadenopathy
There is no definitive treatment (chemotherapy and plasmapheresis for hyperviscosity syndrome)
REFERENCES
Lichtman MA. Chapter 108. Essential monoclonal gammopathy. In: Lichtman MA, Kipps TJ, Seligsohn U, Kaushansky K, Prchal JT, eds. Williams Hematology. 8th ed. New York, NY: McGraw-Hill; 2010
Clinical Genomics: Practical Applications in Adult Patient Care. Chapter 37: Multiple Myeloma and Other Plasma Cell Disorders. Esteban Braggio; Rafael Fonsec.
The MD Anderson Manual of Medical Oncology, 3e. Chapter Chapter 11: Multiple Myeloma and Other Plasma Cell Dyscrasias. Hans C. Lee; Krina Patel; Piyanuch Kongtim; Simrit Parmar; Pei Lin; Muzaffar H. Qazilbash; Sheeba Thomas; Elisabet E. Manasanch